Aqueous dispersion materials containing a functional substance are well known as functional materials, the functional materials including pesticides such as herbicides, and insecticides; medicines such as carcinogenic agents, antiallergic agents, and antiphlogistic agents; and coloring materials such as inks and toners containing a colorant. In recent years, digital printing techniques are progressing remarkably. The digital printing technique is typified by electrophotgraphy and ink-jet printing, and is becoming more and more important as image-forming techniques in offices and families.
Among these techniques, the ink-jet technique has advantages of compactness and less power consumption of the apparatus for direct recording, and the technique is progressing rapidly in image quality by use of finer nozzles and other improvement. In an example of the ink-jet techniques, an ink supplied from an ink tank is heated by a heater in a nozzle to evaporate and bubble, whereby the ink is ejected onto a recording medium to form an image. In another example of the ink-jet techniques, ink is ejected through a nozzle by oscillation of a piezoelectric element.
The inks used in ink-jet techniques are usually aqueous dye solutions. The aqueous dye solutions tend to cause ink bleeding on overlap of colors, or ink feathering along paper fibers at recorded positions on the recording medium. The coloring materials containing a colorant mainly composed of a dye are required to have improved weatherability. For the improvement thereof, Japanese Patent Application Laid-Open No. 5-208548 employs a reactive dye ink. U.S. Pat. No. 5,320,668 utilizes reaction of a reactive pigment and a dye. Japanese Patent Application Laid-Open No. 2000-129184 employs a reactive self-dispersing pigment. However, further improvements are waited for.